Though anitumor antimitotic agents are some of the most successful anticancer agents, such as taxanes, these agents are plagued by numerous drawbacks that are the cause of chemotherapy failure. In Preliminary Studies we have discovered a unique set of antitumor antimitotics that: 1) possess a broad spectrum of potent antitumor activity (60 tumor cell lines at nanomolar GI50); 2) circumvent tumor resistance due to overexpression of P-glycoprotein (MDR) and/or ?III-tubulin, two of the major clinically relevant tumor resistance mechanisms that hinder antitubule activity of the taxanes and other antimitotics; 3) are highly water soluble, thus overcome the lack of water solubility that continue to plague a large number of antimitotics including the newly approved ixabepilone; 4) are selective for tumor cells over normal cells; 5) bind to or near the colchicine-site in tubulin; and 6) are highly efficacious in tumor xenograft without toxicity. The analogs proposed for optimization of the lead compounds are easily synthesized as water soluble salts. The analogs will be evaluated as inhibitors of tumor cells and tubulin assembly in vitro and active compounds will be prioritized for further studies in three xenograft models and in Taxol resistant tumors in vivo murine tumor models. These results will allow the development of pharmacophores that will provide other molecules to be synthesized. The Specific Aims of this project are: 1) to synthesize and optimize the activities of lead compounds; 2) to evaluate the activities of the synthesized analogs as inhibitors of tumor cells in culture and of tubulin assembly and mechanistic studies; 3) to evaluate prioritized, selected analogs in vivo in sensitive and resistant murine tumor models. The broad long term goals of this project are to optimize these novel agents to allow the selection of a candidate or candidates for Phase I clinical trials as antitumor agent(s) to be used alone or in combination with other antitumor agents (including other antimitotics) as well as radiation for the treatment of a broad spectrum of cancers and to fill an unmet need for patients with antitubulin resistant diseases.